“I guess the site gets hacked every now and then.”
You may see obvious clues/signs that your website/hosting account is hacked from time to time, but once a website/hosting account is hacked it remains hacked until you completely cleanup your hacked hosting account. The hack does not come and go every now and then. The hack is permanent until you completely cleanup your hacked hosting account. A hacked website/hosting account has usually been hacked for a very long time (several months and sometimes years) before you are aware that it is hacked. See this forum topic for how to cleanup a hacked hosting account: https://forum.ait-pro.com/forums/topic/wordpress-hacked-wordpress-hack-cleanup-wordpress-hack-repair/